This invention relates to the field of machine process control systems, and, more particularly, to process controllers networking in a manner most suitable for real-time operations control of mailing machine process systems.
Conventionally, high speed mail processing systems have included an envelope singulating and feed mechanism, a scale or other means of determining mailpiece weight, a transport mechanism and a postage indicia printing mechanism, such as a postage meter. Such processing systems have as their objective, the processing of mailpieces in a seriatim manner at the fastest possible rate, through-put rate.
Conventionally, such mail processing systems are configured by establishing individual processing stations and providing synchronized transports for transporting the mailpieces between stations. For example, in one such system a feeder station singulates mailpieces from a mailpiece stack. The respective mailpieces are transported to a scale for weighing. The weight is electronically communicated to a postage meter for setting to the postage print mechanism and the accounting of the corresponding postage. Subsequent to weighing the mailpiece, the mailpiece is transported to a mailing machine print station for indicia printing by the postage meter which is conventionally mounted to the mailing machine.
Processing of a mail stream in the described fashion requires a high degree of coordination between the individual mechanism. Each mechanism is customarily under the controlling influence of its own microprocessor controller. System coordination between the individual system mechanism is accomplished by simple "STOP-GO" signals between the individual mechanism. The "STOP" signal, in most cases, being triggered by a simple electro-mechanical switch and the "GO" signal being electrically triggered by the processing mechanism upon completion of its functional task. For example, upon singulation of a mailpiece from the mailpiece stack, the feeder triggers the transport, either through a mechanical switch or simple "GO" signal from the feeder's microprocessor, to take control over the positioned mailpiece. The transport, responding to the "GO" signal assumes control over the mailpiece for delivery to the scale, placing the feeder in a "STOP" or standby mode. Upon arrival of the mailpiece at the scale, the transport releases control over the mailpiece and triggers a "GO" signal to the scale, thereby placing the transport in a "STOP" of standby mode. The described "STOP-GO" procedure is repeated between the scale, mailing machine transport and postage meter. Variation on this type of system coordination theme are known in efforts to increase the mail process through-put.
In order to improve the through-put of such mailing system, it is known to make the system time dependent. That is, each mechanism is given a discreet time interval to perform its given function before the next mechanism is activated. Time dependent mail processing systems are often provided with "serving-up" ability, i.e., a mailpiece is presented to the next process station just prior to processing completion of the preceding mailpiece.
It has been found that the described system coordination schemes are ill-suited for greater high-speed mail processing systems where such systems are expected to process mixed mailpieces, i.e., a mailpiece stack having substantial variation in envelope dimensions and weights. As applied to such higher speed mail processing systems, it has been found that increases in processing system through-put is adversely effected by an increased presence of process system jamming. Also, in order to accommodate mixed mailpieces, the station process time must be increased.